1. Field of the Invention
The present invention relates to a regulating device which regulates a temperature of a medium.
2. Description of the Related Art
Recently, a semiconductor integrated circuit such as an IC and an LSI requires a high productivity and a fabrication of an ultrafine circuit pattern. Therefore, a rapid and accurate positioning control is necessary. The positioning accuracy heavily depends on the length measurement accuracy by a laser interferometer. In order to achieve the accuracy of nanometer order, the temperature fluctuation of the interferometer optical path needs to be sufficiently suppressed. Therefore, it is necessary to suppress the influence of the temperature change in a clean room where an exposure apparatus is placed or the like, and a medium (fluid) such as air or liquid whose temperature is always stable with respect to the load change of the exposure apparatus needs to be supplied to the exposure apparatus.
In particular, a positioning apparatus which rapidly operates, that is to say, a stage which mounts a reticle or a wafer generates a large heat load for a rapid operation during the exposure process. On the other hand, it does not substantially generate the heat load during the change of the wafer or the reticle and the alignment because of the low velocity operation. Since these operations are alternately performed, the exposure apparatus repeats an abrupt load change.
Japanese Patent Laid-Open No. 11-135429 discloses a fluid supplying apparatus which supplies fluid to an exposure apparatus. The fluid supplying apparatus disclosed in Japanese Patent Laid-Open No. 11-135429 is configured to detect the temperature of air which is supplied to the exposure apparatus and control the temperature by operating a Peltier device or a heater. Then, the air supplied to the exposure apparatus is returned to the fluid supplying apparatus by a feedback duct. Thus, the heat load is recovered via a fan or a cooling machine and the temperature control is performed by the Peltier device or the heater described above.
Japanese Patent Laid-Open No. 2006-12564 discloses a cooling apparatus which suppresses the influence of the load change. The cooling apparatus disclosed in Japanese Patent Laid-Open No. 2006-12564 is configured to have a fuel cell as a load, recover a generated heat by flowing cooling water to the fuel cell, and recover the heat of the cooling water by a heat exchange of the cooling water and the heated water by a heat exchanger. At that time, it regulates the flow rate of the heated water by changing the driving performance of a pump based on the temperature difference of the heated water between an entrance and an exit of the heat exchanger and the flow rate of the heated water, and operates so that the temperature of the cooling water outputted from the heat exchanger is a predetermined value. The flow rate of the heated water is detected by a flow sensor which is attached at the output side of the pump.
In the conventional technology, the cooling heat quantity required to change the temperature at the exit of the heat exchanger to a predetermined value is calculated based on the temperature of the cooling water which flows into the heat exchanger with the heat load. The flow rate of the heated water is regulated by changing the driving performance of the pump so that the actual cooling heat quantity calculated based on the temperature difference of the heated water at the entrance and the exit of the heat exchanger and the flow rate of the heated water is equal to the calculated cooling heat quantity. Thus, the influence of the load change is suppressed.
Japanese Patent Laid-Open No. 11-135429 discloses a temperature control method which controls the temperature in a chamber of an exposure apparatus. However, the temperature control method disclosed in Japanese Patent Laid-Open No. 11-135429 performs a feedback control of the temperature of air which is supplied to the exposure apparatus. Therefore, if the load of the exposure apparatus is abruptly changed, a large temperature error is generated because of a response delay. Thus, a temperature control with high accuracy for an abrupt and large load change in the exposure apparatus cannot be performed.
Japanese Patent Laid-Open No. 2006-12564 discloses a control apparatus which regulates the flow rate of cooling water. The control apparatus in Japanese Patent Laid-Open No. 2006-12564 performs a control so that the cooling heat quantity required to set the temperature at the exit of the heat exchanger calculated based on the temperature of the cooling water which flows into the heat exchanger to a predetermined value is equal to the cooling heat quantity calculated based on the temperature difference of the heated water at the entrance and the exit of the heat exchanger and the flow rate of the heated water.
However, actually, there is a case where the temperature at the exit of the heat exchanger does not be the predetermined value. This is because there is a measurement error of the flow sensor or the temperature sensor or an error of the heat exchange efficiency in the heat exchanger, or the like. Therefore, in the conventional technology, a temperature control with high accuracy for an abrupt and large load change in an exposure apparatus cannot be performed.
There are a Karman vortex method, an ultrasound waver method, an impeller method, an electromagnetic method, and the like, as a detecting method of a flow sensor. Most of the flow sensors of the Karman vortex method or the impeller method are small and inexpensive. However, a detecting range of the flow sensors is limited and the detecting accuracy in a low flow rate is also a problem. For example, the flow sensor whose accuracy is equal to ±3% F.S and detecting range is 8 L/min to 50 L/min cannot detect the flow rate equal to or lower than 8 L/min. Because the accuracy is ±1.5 L/min, the detecting accuracy at the minimum flow rate is 8±1.5 L/min. Therefore, the error ratio with respect to the flow rate of 8 L/min is ±12.5%, which is extremely large.
In the conventional technology, the flow rate of the heated water is significantly changed by regulating the driving performance of the pump because of the change of the heat load. In other words, the flow rate of the heated water is reduced when the heat load is small. On the other hand, the flow rate of the heated water is regulated so as to be increased when the heat load is large. The flow rate of the heated water is detected by a flow sensor. However, as described above, because of the detecting limitation and the detecting error of the flow sensor, in particular, a flow rate detecting error is large in the case where the flow rate is low, and in some cases, the flow rate cannot be detected. Therefore, the operation of the temperature control is unstable. Thus, the conventional technology cannot perform a temperature control with high accuracy with respect to an abrupt and large load change in an exposure apparatus.